SOLUTION: My question is: Minoxidil is a drug that has recently proven to be effective in treating male pattern baldness. Water must be added to 20 mL of a 4% solution to dilute it to a 2%

Question 159535: My question is:
Minoxidil is a drug that has recently proven to be effective in treating male pattern baldness. Water must be added to 20 mL of a 4% solution to dilute it to a 2% solution. How many milliliters of water should be used? (Hint: Water is 0% minoxidil.) The answer is 20 mL, but I cannot put it into an ordered equation. My mind knows the answer, but I cannot formulate it on paper. This is my first college algebra class and my mind has difficulty with this kind of logic. Please help.
Answer by ptaylor(2198) (Show Source): You can put this solution on YOUR website!
Let x=amount of water needed
Now we know that the amount of pure minoxidil in the 20ml of the 4% solution(0.04*20) plus the amount of pure minoxidil in the water (0) has to equal the amount of pure minoxidil in the final mixture(0.02*(20+x)). So our equation to solve is:
0.04*20=0.02(20+x) get rid of parens and simplify
0.8=0.4+0.02x subtract 0.4 from each side
0.8-0.4=0.4-0.4+0.02x collect like terms
0.4=0.02x divide each side by 0.02
x=20 ml -----amount of water needed
Hope this helps---ptaylor

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